$7-34$ A student team is to design a human$-$powered submarine for a design competition. The overall length of the prototype submarine is $4\mathrm{.}85$ m $,$ and its student designers hope that it can travel fully submerged through water at $0\mathrm{.}440\frac{m}{s}.$ The water is freshwater $($a lake$)$ at $T=15C.$ The design team builds a one$-$fifth scale model to test in their university's wind tunnel $($Fig$.$ P$7-34).$ A shield surrounds the drag balance strut so that the aerodynamic drag of the strut itself does not influence the measured drag. The air in the wind tunnel is at $25C$ and at one standard atmosphere pressure. At what air speed do they need to run the wind tunnel in order to achieve similarity? Answer: $30\mathrm{.}2\frac{m}{s}$